Patent GB-425112-A (GB)
Title: Improvements in and relating to two-stroke internal combustion engines
IPC: F02B75/02
Filed: 1933-09-02
Abstract: 425,112. Two-stroke engines; lubricating passages. EDLIN, G. S., 59, Portsmouth Road, Surbiton, Surrey. Sept. 2, 1933, Nos. 24424/33 and 21869/34. [Class 7 (ii)] [See also Group XXXIV] In a two-stroke cycle engine opposed pistons work in cylinders parallel to and radially equidistant from a hollow central shaft. The drive is transmitted through rollers on the piston-rods engaging cams on the shaft, guide members being provided for preventing lateral movement of the piston rods. Rotary pumps supply scavenging and charging air to pistoncontrolled ports at one end of the cylinders, and cooling air around and through the hollow piston rods, while the opposing piston controls the exhaust ports. Cylindrical casings 21, 22 acting as housings for the cam-riiig members are separated by a polygonal member 23 around which are spaced the four cylinders 24 having flanged ends bolted to the endplates closing the casings. The outer end of casing 22 is closed by inner and outer plates 31, 35 forming a blower housing. Driving-gear.-The hollow piston rods 40, rigidly secured to the pistons, pass with slight clearance through packing glands in a plate 24<c> closing the cylinder ends. Their movement is transmitted through conical rollers 41, 42, mounted on opposite ends of a hollow pin 73 traversing the end of each piston rod, and having their vertices on the axis of the shaft 36, to inner and outer cam-tracks 45, 46 integral with webs 44, stiffening ribs 47 and a sleeve 43 keyed to the shaft 36. Crossheads, or slipper-blocks 51, are formed integrally with the piston-rod ends, and work in guides 52, 53 integral with the end-closure plates 27 of the housings 21, 22, and extending in a direction parallel to the shaft in the form of segmental box-shaped members, their walls forming bearing surfaces for the cam tracks 45, 46 as well as for the slipper-blocks 52. The engaging surfaces of the blocks and guides are inclined so that the radially inward thrust opposes the outward thrust due to the rollers 41, 42. Retaining flanges 53b in alignment with the surface 53<a> take up excessive inward thrust. The inner rollers 41 are engaged by a third cam-track 48 opposite to the track 45 and similarly supported from the sleeve 43. This track comes into operation in starting up the engine. The housings 21, 22 act as bearings for the outer end of the outer cam tracks 46. The cam profiles may be such as to give rapid expansion and slower compression with a sharp peak at the point corresponding to the inner dead-centre, the curve in the region of the outer dead-centre being flattened to give long duration to the opening of the inlet and exhaust ports. The outer dead-centre may be unsymmetrically placed with respect to the inner dead-centre giving, for example, an expansion stroke two-thirds of the compression stroke in duration. The cams at the two ends of the engine may also be displaced relative to each other so that the exhaust ports open before the inlet ports. Lubricating passages.-Oil is delivered to orifices 80 in the guide walls 52, and thence to grooves 83 in the slipper face parallel to its direction of movement ; radial channels 84 convey the oil to channels 86 in the wall of the hollow pin 73, these communicate by openings 87 with the roller bearings 75 for the rollers 41, 42. A pump delivering its maximum pressure as the orifices 80 and grooves 83 come into register is used, this being arranged to occur when the piston rod has completed about 20 per cent of its outward stroke. Cylinders, pipes and passages for ; pumps.- The cylinder bores are of slightly larger diameter at each end than in the centre, permitting radial movement of the piston rings for the purpose of clearing the grooves. A pair of Roots' blowers, driven by toothed gearing from the shaft 36 and housed in the end casing 35<a>, delivers air to the spaces 57 between the double walls of the casing 22. The exhaust controlling pistons are similarly cooled either by a blower or by transfer passages between the casings 21, 22. An intake manifold 58 is formed by cylindrical and annular flanges integral with the end plate 27, one flange being bored for the passage of the cylinders 24. Oblique inlet ports 59 admit scavenging and charging air to the cylinder. After passage of the piston on its inward stroke, air from the manifold 58 traverses and cools the hollow piston rod. An exhaust manifold 61 is formed around the other ends of the cylinders which are provided with a water cooling system comprising jackets 25, and inlet and outlet orifices 64, 65. Fuel pumps 67 are mounted on the polygonal centre piece 23 and are actuated by cams mounted on the central shaft. Thrust bearings are provided at one end only of the shaft 36, the bore of which is unobstructed for the passage of natural or forced draught.